Smouldering mega-fires in the Earth system

I just gave the presentation "Smouldering mega-fires in the Earth system" at the conference Exploring the Mega-fire Reality, Florida State University. It went well very,  good questions (~8) from audience and great feedback. The abstract is below.

Smouldering mega-fires in the Earth system

Abstract
Smouldering fires, the slow, low-temperature, flameless burning of organic matter release anually at a global scale the equivalent to ~15% of man-made carbon emissions. It accounts for the accidental burning of fossil fuels, including natural as well as antropogenic causes. Very large fires of organic matter (mostly in peatlands) have burnt since past millennia for long periods of time (months, years, decades; the longest continuously fires on Earth). Flaming forest fires have been the central focus of most research, but smouldering mega-fires are paramount to the Earth System and have received very little attention. Smouldering is the most persistent type of combustion phenomena; the easiest to ignite, and the most difficult to suppress. Peat fires propagate slowly (~1 mm/min) through organic layers of the ground and can reach depth >5 m when large cracks or a natural piping system exists. It is a 3-dimensional phenomena, spreading deep into the soil and over extensive areas of land. The depth of burn is given by the location of the inert layer, very moist layer (>125%MC) or firefighting attempts. Observed depths of burn reported in the literature range from 0.1 to 5 m, with the average around 0.5 m (=75 kg/m2 of fuel consumption). This is 40 to 90 times larger than flaming fires. In terms of fuel consumption, these are mega-fires. This is of great concern given that world peatlands contain more terrestrial carbon than the forests or the atmosphere. Compared to the natural carbon flux to the atmospherefrom from peatland degradation, smouldering fires is 3,000 times faster. These wildfires burn fossil fuels and thus are a carbon-positive fire phenomenon via soil moisture deficit and self-heating. Warmer temperatures at high latitudes are resulting in more frequent Artic fires and unprecedented permafrost thaw.

Smouldering mega fires are back in Russia: burning peat

Remember the Russian wildfires last summer that choked the city of Moscow and other regions? These were smouldering mega fires burning for several weeks and caused by the slow burning of dry peatlands. See here for an introduction to smouldering combustion.

Unfortunately, they are back this summer. Last week, they were several flaming fires burning in the region of Moscow. After flames were extinguished, the peat was seen to smoulder. Given the pollution, environmental and climate disaster that the smouldering mega fires brought last summer, the worry is that they might burn for months in 2011 as well. Given the extreme difficulty of suppressing smouldering fires when these have already grown out of proportions, the Fire Service is afraid that the fate might be in the hand of the rain.

In the meantime, Greenpeace reported about 20 peat fires in Russia.

PD: There are currently smouldering mega fire burning in North Carolina, Georgia and Indonesia.

Smouldering Subsurface Fires in the Earth System

Given the attention paid during the last month to peat fires because of the dramatic events taking place in Russia this summer [*], some might be interested in learning more about smouldering fires. Bellow is the abstract of a review paper on peat fires that I am presenting at an forest fire research conference in November.

NOTE: A recent poster presented at the European Geoscience Union. Vienna, May 2010 is on the right of the post. Click on it for pdf.


[*] Post: the New York Times featured some of my comments in that 12 Aug article.


[*] Post: The NYTimes.com blog Dot Earth features my work and links to this blog in the article "Fire Down Below" on smouldering peat fires.






[*] Post:  Quoted in the oneearth.org article "Why We Should Care About Forest and Peat Fires in Russia" by Steven Apfelbaum.


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Smouldering Subsurface Fires in the Earth System

Dr Guillermo Rein

BRE Centre for Fire Safety Engineering

University of Edinburgh

G.Rein@ed.ac.uk

To appear in VI International Conference on Forest Fire Research, Coimbra, November 2010.


Abstract
Smouldering fires, the slow, low-temperature, flameless form of combustion, are an important phenomena in the Earth system, and the most persistent type of combustion. Large smouldering events are rare at the local scale but occur frequently at a global scale. Only after the study of the 1997 extreme haze event in South-East Asia, the scientific community recognised the environmental and economic threats posed by subsurface fires. The haze was caused by the spread of vast smouldering peat fires in Indonesia, burning below the surface for months during the El Niño climate event. It has been calculated that the 1997 fires released between 0.81 and 2.57 Gton of carbon gases (13–40% of global emissions). Smouldering fires propagate slowly through organic layers of the forest ground (shallow fires, typically 0.25 to 2 m) and can reach deeper horizons if large cracks, natural piping or artificial channel systems exist (deep fires). Biomass capable of sustaining these fires are logs, litter, duff, humus, peat, coal seams and soils with a significant organic fraction, which total carbon pool exceeds that of the Earth’s forests or atmosphere. Once ignited, they are particularly difficult to extinguish despite extensive rains, weather changes or fire-fighting attempts, and can persist for long periods of time (months, years) spreading deep and over extensive areas of forest subsurface. Indeed, these are the oldest continuously burning fires on Earth (up to 6,000 years). Differences with flaming fires are important in terms of dynamics, emissions and suppression. Whereas flaming fires result in superficial heating of the soil, smouldering leads to sterilization and loss of mass above 90% (a layer of 5 m is reduced to 30 cm). Moreover, these fires are difficult to detect with current remote sensing methods because the chemistry is significantly different, their thermal signature is much smaller, and the plume is much less buoyant than flaming fires. Smouldering fires have important implications for climate change. Warmer temperatures at high latitudes are resulting in more frequent Artic fires and unprecedented permafrost thaw is leaving large soil carbon pools exposed to smouldering fires for the fist time since ancient times. This paper revises the current knowledge on smouldering fires in the Earth system regarding ignition, spread patterns and emissions, and presents a series of case studies on real fires (2006 Rothiemurchus, 2008 Evan’s Road and 2009 Las Tablas de Daimiel).

Keywords: smoldering, flameless combustion, peat, coal, underground fires